Design and control of chemical reactors in recycle systems

Alexandru C. Dimian, Costin S. Bîldea, Anton Kiss

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


To comply with modern requirement's, as flexibility in production, high efficiency of raw materials, reduced inventories and down-to-zero waste, both design and control of reactors in recycle systems should be integrated at an early design stage. The paper presents a synthesis of a series of original researches in this field in the last years. The generic structure is the Reactor-Separator-Recycle system. It is argued that the reactor volume should be higher than a minimum value in order to ensure feasible operation. In contrast with stand-alone reactors, multiple steady states are possible solely due to the effect of material recycles, but non-isothermal operation may bring even more sophisticated non-linearities. Another topic is the intricate relation between plantwide control structures and reactor design, an aspect largely ignored by now both by designers and control engineers. It is demonstrated that the so-called snowball effect (high sensitivity) is merely a matter of reactor design than control. A clear distinction is made between self-regulation and controlled-regulation structures in relation with the stoichiometry of the reaction network and the make-up policy of reactants. In general, using the recycle flow rate to manipulate the production rate is a good design practice, better than fixing the fresh feeds of reactants. However, in some cases, namely for some complex reactions, the simple self-regulation feed policy is workable. In addition it may ensure a desired selectivity pattern. The paper presents briefly other contributions, as the minimisation and control of waste and impurities by systemic analysis, as well as the optimal use of energy in highly exothermal reactions.

Original languageEnglish
Pages (from-to)585-594
Number of pages10
JournalRevista de Chimie
Issue number8
Publication statusPublished - 2004


  • Recycle systems
  • Selectivity pattern
  • Snowball effect

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science (miscellaneous)
  • Engineering(all)
  • Surfaces, Coatings and Films
  • Materials Chemistry


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